The present invention relates to a resin for hot melt adhesives used for sanitary materials, for packaging, for bookbinding, for fibers, for woodworks, for electricity materials, for can manufacturing, for construction, for bag making, etc. More particularly, the present invention relates to a new polyolefin resin for hot melt adhesives superior in heat resistance and flowing ability at high-temperature and superior in adhesive property to lowly polar substances.
Application of the hot melt adhesives used in adhesion melting high polymer by heat and adhering with hot melt method is expanding in various fields by the reason of superiority in high speed coating, rapid hardening, no solvent required, barrier property, energy-saving and economic rationality, etc. As conventional hot melt adhesives, a resin produced by blending adhesive capacity applying resin and plasticizer to a base polymer such as natural rubber, ethylene-vinyl acetate copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer is mainly employed. However, the aforesaid base polymer contains many double bonds. Therefore, as the resin for hot melt adhesives by the use of the foregoing base polymer, there were problems such as inferior thermostability in heating, occurrences of oxidation, gelation, decomposition and coloration in coating and a change of bonding strength in adhesive part with the passage of time. Moreover, there was drawback to be inferior in adhesive property with lowly polar substances such as polyethylene or polypropylene. Regarding a resin for hot melt adhesives to these lowly polar substances, there was conventionally a resin using polypropylene, etc. as the base polymer. However, although these resins are superior in thermal stability, there were problems of too high degrees in hardness of the base polymer, necessity of coating at high-temperature covering poor flowing ability, inferior thermostability at high-temperature and insufficient adhesive property.
Overcoming the foregoing problems or drawbacks in the resin for hot melt adhesives, an object of the present invention is to provide a polyolefin resin for hot melt adhesives that is superior in thermostability or flowing ability at high-temperature, in adhesive property to lowly polar substances and in heat resistance of the adhesion face.
The present invention was completed by zealously investigating and finding that a polyolefin resin for hot melt adhesives comprising a specific propylene polymer and an adhesive capacity applying resin enables to achieve the object of the invention. That is, the present invention provides the following polyolefin resins for hot melt adhesives.
[1] A polyolefin resin for hot melt adhesives comprising [I] a propylene polymer in an amount of 20 to 99 mass %, and [II] an adhesive capacity applying resin in an amount of 80 to 1 mass %, wherein [I] the propylene polymer satisfies the following requirements of:
(1) a meso pentad fraction (mmmm) is from 0.2 to 0.6; and
(2) a racemic pentad fraction (rrrr) and (1xe2x88x92mmmm) satisfy the following relation:
[rrrr/(1xe2x88x92mmmm)]xe2x89xa60.1.
[2] The polyolefin resin for hot melt adhesives as defined in the item [1] wherein [I] the propylene polymer satisfies the following requirement of:
(3) an intrinsic viscosity [xcex7] measured at 135xc2x0 C. in tetralin is from 0.01 to 2.0 deciliter/g.
[3] The polyolefin resin for hot melt adhesives as defined in the item [1] or the item [2], wherein [I] the propylene polymer satisfies the following requirement of:
(4) an amount of a component which is eluted at 25xc2x0 C. or lower through temperature rise chromatography (W 25) is from 20 to 100 mass %.
[4] The polyolefin resin for hot melt adhesives according to any one of the items [1], [2] or [3], wherein [I] the propylene polymer is polymerized by the use of a metallocene catalyst containing a promoter and a transition metallic compound in which a cross-linking structure is formed via two cross-linking groups.
[5] The polyolefin resin for hot melt adhesives according to any one of the items [1], [2], [3] or [4] wherein [II] the adhesive capacity applying resin is a hydrogenated petroleum resin.